The effects of some abiotic factors (pre-incubation condition, floating in 1% NaOCL, temperature and photoperiod) was investigated on the hatching response of Daphnia similis ephippial eggs collected from live food ponds in cultivation centre of Gorgan. After isolation, the eggs were kept in dry and wet conditions at 4°C for 2 months in darkness. Following the pre-incubation period, the eggs in each group were subdivided into 2 parts and treated with1% NaOCL and distilled water. The effect of temperature levels (20˚C, 25˚C and 30˚C) and photoperiod levels (12L: 12D and 24L: 0D) were identified on the hatching of eggs in AdaM medium during 15 days. Results indicated that the exposure of wet eggs of Daphnia similis to 12-hour photoperiod and 20˚C after soaking in 1% NaOCL, increased the maximum rate and speed of hatching. These ephippial eggs significantly reacted more rapidly while keeping in wet condition at 20˚C but no significant difference (P > 0/05) in shortening time until hatch was observed among different levels of photoperiod and floating in 1% NaOCL.